The present invention relates to an electric rotary actuator. More particularly it relates to an electric rotary actuator, particularly for controlling a throttle cross-section in a line conducting operating fluid of an internal combustion engine which has a housing enclosing a motor actuator with windings and magnetic poles and a rotatable magnetic armature connected to a throttle member. Such rotary actuators are known, for example, from German Offenlegungsschrift 37 28 589 (=U.S. Ser. No. 203 800) and conventionally consist of an electric motor actuator, on the protruding, extended armature shaft of which a throttle member is mounted which is arranged in a fluid-conducting line. This rotary actuator thus requires a relatively large constructional space and additional seals between throttle member and motor actuator in order to prevent unwanted fluid leakages.